Draft v1.0 June 13 2007
Title: Coronal holes boundaries evolution
Authors
Maria Madjarska, Max-Planck-Institut für Sonnensystemforschung,
Germany (madjarska@mps.mpg.de)
L. Harra, Mullard Space Science Laboratory, UCL, UK
T. Wiegelmann, Max-Planck-Institut für Sonnensystemforschung, Germany
D. Innes, Max-Planck-Institut für Sonnensystemforschung, Germany
Participating instruments:
Hinode/EIS
Hinode/XRT
Hinode/SOT
SoHO/CDS
SoHO/SUMER
SoHO/MDI
STEREO/SECCHI
TRACE
Scientific justification:
Because of the different rotational profiles in the corona and at
photospheric level and the fact that coronal hole boundaries separate two
topologically different magnetic field configurations (open and closed),
coronal hole boundaries are presumably the region where a continuous
opening and closing of magnetic field lines takes place. This
reconfiguration is believed to happen through magnetic reconnection between
the open magnetic flux of the coronal hole and the closed one of the quiet
Sun. Madjarska, Doyle & van Driel-Gesztelyi (2004, ApJ, 603, 57) found the
first evidence for magnetic reconnection along coronal hole boundaries
using SUMER observations in spectral lines formed at transition region
temperatures. Wang & Sheely (2004, ApJ, 1196), however, believe that the
reconnection takes place very high in the solar atmosphere (~ 2.5R), and
that it occurs continuously in the form of small, stepwise displacements of
field lines. A very important part of the present research will be the
search for the origin of the slow solar wind. The helmet-streamer loops are
considered as a possible source of the slow solar wind but with the major
component coming from the coronal hole boundaries. With this present
study, we want to observe equatorial coronal hole boundaries in order to
find spectroscopic signatures of the physical processes which take place
using simultaneously SUMER/EIS observations which will permit observations
in spectral lines covering a large temperature range (from 40 000 K to a
few million degrees). TRACE and XRT/Hinode will provide high resolution
imaging in EUV and X-ray, respectively. MDI and SOT magnetic field data
are crucial for this study. The study will combine spectroscopy and
imaging and thanks to the high resolution vector magnetograms we can derive
the geometry and the 3D scaling via magnetic field extrapolation
(Wiegelmann, 2004, Solar Phys. 219, 87). The STEREO EUV and coronagraph
observations will provide the necessary observational material for studying
the connection between the coronal hole boundaries evolution and the slow
solar wind generation.
Target
Equatorial coronal hole boundaries at three consecutive positions: at disk
center, W40-W50 degrees and limb. Additionally quiet Sun region
observations before or after in order to be used as a reference.
Observing details
SoHO:
SUMER: simultaneous observations in chromospheric, transition region and
coronal lines. POC: M.S. Madjarska
CDS: high cadence rastering at coronal hole boundaries in several
transition region and coronal lines. POC: M.S.Madjarska
MDI: HR when is possible or FD 1 minute cadence. POC: M.S.Madjarska
TRACE: 171 A (no less than 30 sec exposure time) with context images in
1700 channel; 768 x 768 pixels FOV, as high as possible cadence and
constant exposure time (except when is changed by the Automated Exposure
Control); POC: M.S. Madjarska
Hinode:
EIS: raster image followed by slot observations in He II, Si VII, Mg VII,
Fe VIII, Fe X, Fe XI, Fe XII, Fe XIII, Fe IVXIV, Fe XV, Fe XVI POC:
L. Harra & M. Madjarska
SOT: Ca H and G band, SP fast maps, magnetic field, Halpha. POC: TBD
XRT: Reduced field-of-view images with Al-poly filter and G-band images. As
high as possible cadence. POC:TBD
STEREO: High cadence 171 A and 195 A, White light images with both COR1 and
COR2. POC: M. Madjarska
Observing period
Preferential observing period October 22 - November 2 (during the SUMER
campaign)
A Deputy JOP Leader, Davina Innes, will be present at Goddard during this
period of time.